This application pertains to the art of valves and, more particularly, to bypass valves. The invention is particularly applicable for use with liquid fuel filters and will be particularly described with reference thereto. However, it will be appreciated that the invention has broader aspects, and can be used with other fluid filters and in other fluid systems having bypass valves.
Fuel filter assemblies commonly have a bypass valve which opens when the filter element becomes clogged. It is common to provide a signal light which is turned on when the bypass valve opens for indicating a clogged filter condition. It is also common to provide another signal device on the filter assembly itself which locks in an indicating position and cannot be reset without removing the filter element.
Prior patents related to the subject matter of this application include Downey U.S. Pat. No. 3,442,384; and Sample U.S. Pat. No. 3,451,551 and U.S. Pat. No. 3,487,929.
In many prior arrangements of the type described, the bypass valve cracks open at a relatively low pressure and the signal light does not go on until such valve is cracked open so that some fuel is already being bypassed.
It would be desirable to have an arrangement wherein the signal light would go on prior to complete clogging of the filter for indicating that clogging of the filter is impending. The filter element can then be replaced before the bypass valve opens.